Directional valve

Abstract

 A directional valve (12, 14) intended for respiratory devices (2), comprising a valve body (18) and a valve seat (16) whose contact surface with the valve body (18) is primarily horizontal, is described. In order to enhance and reinforce the directional valve's operation, the valve body (18) contains a ferromagnetic material, preferably permanently magnetised, a coil (22) is magnetically connectable to the valve body (18), a source of current (24) is connected to the coil (22), and a control unit (26) controls the source of current (24) in order to regulate current through the coil (22) and magnetically couple the coil (22) to the valve body (18, in one or both of the closing and opening directions.

Description

[0001] The present invention relates to a directional valve according to the preamble to claim 1.

[0002] Directional valves are used in respiratory devices, anaesthetic machines in particular, to channel the direction of flow. One directional valve is generally installed in the anaesthetic machine's inspiratory line and one directional valve in its expiratory line. The directional valves should not affect expiratory resistance and inspiratory resistance for the patient nor interfere with measurements of flow in the anaesthetic machine. One way to meet these conditions has been to devise directional valves with the lowest possible opening pressure. They are therefore generally devised as disk valves, i.e. the directional valve has a disk-shaped valve body that rests loosely on a valve seat.

[0003] However, this type of directional valve has disadvantages. One disadvantage develops because moist gas is present in the anaesthetic machine. The valve body could become wet, leading to surface tension that increases the opening pressure.

[0004] Other disadvantages are due to the shape of the valve body. If it is devised as a soft, lightweight disk, retrograde leakage could occur. Moreover, the valve body could be deformed enough by high back pressures to be pushed down into the valve opening. This would naturally be a serious development, since the directional valve would then stop working. Retrograde leakage can be reduced by the use of a heavier directional valve, but this would naturally increase the valve's opening pressure, and the valve body might then start wobbling. Stiff valve bodies (usually ceramic disks) could start to leak because of the deposition of calcium particles etc. on the valve seat.

[0005] One object of the invention is to achieve a direction valve that solves the aforementioned problems.

[0006] One such directional valve is achieved according to the invention when the directional valve is devised as is evident from the characterising part of claim 1.

[0007] Advantageous refinements and embodiments are evident from the subordinate claims of claim 1.

[0008] When the valve body contains a ferromagnetic material and two coils are arranged with one coil on top of the valve body and one coil underneath the valve body, the valve body can be made to press against the valve seat or alternately lift off the valve seat by regulating the current flowing through the respective coil.

[0009] The directional valve can be operated as a servo system when the valve body contains a permanently magnetised material and a coil encircles the valve body and valve opening (to achieve the strongest possible magnetic coupling between the coil and the valve body). When the directional valve is to be in the closed position, a current is applied across the coil, generating a magnetic field that presses the valve body harder against the valve seat. This would accordingly reduce the risk of leakage.

[0010] When the directional valve is to be in the open position, the current is reversed, causing the electromagnetic field to lift the valve body. A minimal opening pressure is then achieved.

[0011] In the event of any loss of current, the directional valve would operate in the same way as in the prior art. Directional valve operation is not interrupted. This is an important safety feature when the valve is used in anaesthetic machines and other respiratory devices.

[0012] Current through the coil is regulated from a source of current that is regulated, in turn, by a control unit. In principle, the control unit could regulate the source of current in such a way that directional valve operation parallels the respiratory devices's inspiratory and expiratory phases. The directional valve in the inspiratory line would then be open during inspiration and closed during expiration (and the reverse for the directional valve in the expiratory line). However, this kind of simplified regulation is only possible in certain limited conditions, e.g. no bias flow is used and the patient is not breathing spontaneously.

[0013] More refined regulation, tailored to different phases of respiration, e.g. during anaesthesia, is possible. The control unit can therefore be devised to control the source of current by sensing the valve body's position. This can be achieved by inductive sensing of the coil. Alternately, the EMF generated by the valve body's movements can be sensed and employed for controlling the source of current. Any deformation of the valve body can even be sensed from changes in inductance.

[0014] Other parameters can also be used for regulation. For example, the pressure gradient between the inlet and outlet sides of the directional valve and flow through the directional valve. These parameters can be obtained either by devising the directional valve with a pressure gauge or a flow meter or by utilising measurement signals from existing pressure gauges or flow meters in the respiratory device.

[0015] The directional valve according to the invention will now be described in greater detail, referring to the figures.

FIG. 1 shows a respiratory device incorporating directional valves according to the invention;

FIG. 2 shows a first embodiment of the directional valve; and

FIG. 3 shows a second embodiment of the directional valve.

[0016] FIG. 1 shows a respiratory device 2 connected to a patient 4, in the conventional, known fashion, by an inspiratory line 6, a patient line 8 and an expiratory line 10. The respiratory device 2 can e.g. consist of an anaesthetic machine, and the patient line 8 can consist of a tracheal tube and Y piece.

[0017] A first directional valve 12 is arranged in the inspiratory line 6 (or between the inspiratory line 12 and the patient line 8), and a second directional valve 14 is arranged in the expiratory line 10 (or between the expiratory line 10 and the patient line 8).

[0018] The function of the directional valves 12, 14 is mainly to achieve one-way passage of gas through the lines 6, 8, 10. So they must not allow any retrograde leakage. At the same time, it is undesirable for the directional valves 12, 14 to create any additional respiratory resistance for the patient 4 during inspiration and expiration. They must therefore open easily in the forward direction.

[0019] FIG. 2 shows a first embodiment of the first directional valve 12 (the second has an identical construction). In this instance, the inspiratory line 6 is connected to the inlet side of the first directional valve 12, and the patient line 8 is connected to the outlet side of the first directional valve 12. The first directional valve 12 has an essentially horizontal valve seat 16. A valve body 18 rests on the valve seat 16. In this embodiment, the valve body 18 is disk-shaped, but other designs are possible. The surface of the valve body 18 in contact with the valve seat 16 should be made of a soft material. A hood 20 encircles the valve seat 16 and the valve body 18. The hood 20 is advantageously transparent to permit visual inspection by the operator.

[0020] A coil 22 surrounds part of the first directional valve 12 for magnetic coupling to the valve body 18 that contains, or consists of, a permanently magnetised ferromagnetic material. When a current is applied to the coil 22 from a source of current 24, the valve body 18 is either pressed against the valve seat 16 or lifted off the valve seat 16, depending on the direction of current in the coil. The directional valve's 12 basic functions can accordingly be enhanced without loss in the event of a power failure. This is extremely important to patient safety.

[0021] The source of current 24 is regulated by a control unit 26 on the basis of suitable control parameters. Some of these control parameters can be obtained from changes in EMF, induction etc. in the coil 22 occurring when the valve body 18 is affected by gases in the lines 6, 8. Determination of these parameters can be performed by e.g. measuring voltage across the coil 22 with a voltmeter 28 and sending the measured value to the control unit 26. (Alternately or as a complement, current in the coil 22 can also be measured and the measured value sent to the control unit 26.)

[0022] Back now to FIG. 1. The control unit 26 in the depicted embodiment is integrated into the respiratory device 2 and controls a first source of current 24A for regulating the first directional valve 12 and a second source of current 24B for regulating the second directional valve 14. Alternately, a separate control unit (in the form of a microchip or the equivalent) can be integrated into the respective directional valve 12, 14.

[0023] Additional opportunities for obtaining control parameters are provided with a first flow meter 30 in the inspiratory line 6, a second flow meter 32 in the expiratory line 10, a first pressure gauge 34 in the inspiratory line 6, a second pressure gauge 36 in the patient line 8 and a third pressure gauge 38 in the expiratory line 10. Flow through the respective directional valve 12, 14 or the pressure gradient between the inlet and outlet sides of the respective directional valve 12, 14 can be determined and used by the control unit 26 for regulating the directional valves 12, 14.

[0024] Even here, the flow meters and pressure gauges 30, 32, 34, 36, 38 can consist of components integrated into the directional valves 12, 14 or of components in the respiratory device 2 (or any combination thereof).

[0025] Regulation is suitably performed in such a way that the control unit 26, via the sources of current 24 and with the aid of the parameters, regulates the directional valves 12, 14 by reinforcing their natural positions (open-closed) in every phase of the respiratory cycle. For many applications, the control unit 26 can suitably be supplied even with information from the respiratory devices's control system on the respiratory cycles etc. Alternately, the control unit 26 can even be an integral part of the respiratory device's 2 control and regulatory system.

[0026] FIG. 3 shows a second embodiment of the directional valve 12. As in the first embodiment, the inspiratory line 6 is connected to the inlet side of the directional valve 12, and the patient line 8 is connected to the first directional valve's 12 outlet side. The first directional valve 12 has a mainly horizontal valve seat 16. A disk-shaped valve body 18 rests on the valve seat 16. The valve body 18 should be made of a soft material at points at which it is in contact with the valve seat 16. A hood 20 encircles the valve seat 16 and valve body 18. The hood 20 is advantageously transparent to permit visual inspection by the operator.

[0027] However, in this second embodiment, the direction valve 12 contains a first coil 40, arranged below the valve body 18, and a second coil 42, arranged above the valve body 18. The valve body contains, or consists of, a ferromagnetic material.

[0028] A current can be applied to the first coil 40 from a first source of current 44, and a current can be applied to the second coil 42 from a second source of current 46. The sources of current 44, 46 are regulated by a control unit 26 on the basis of suitable control parameters in the same way as in the first embodiment. These parameters can be obtained from a voltmeter 28, straight from the sources of current 44, 46 or in some other way described above. However, the sources of current 44, 46 are regulated differently, since current is alternately applied to the first coil 40 and the second coil 42 respectively.

[0029] Other embodiments of the directional valves ate possible. For example, the coil(s) can be located in other ways with retention of the same functions.

Claims

1. A directional valve (12, 14) intended for respiratory devices (2), comprising a valve body (18) and a valve seat (16) whose contact surface with the valve body (18) is primarily horizontal, characterised in that the valve body (18) contains a ferromagnetic material, at least one coil (22; 40, 42) is magnetically connectable to the valve body (18), a source of current (24, 24A, 24B; 44, 46) is connected to the coil (22; 40, 42) and a control unit (26) regulates the source of current (24, 24A, 24B; 44, 46) in order to control current through the coil (22; 40, 42) so the coil (22; 40, 42) is magnetically coupled to the valve body (18) in one of the closing and opening directions.

2. The directional valve according to claim 1, characterised in that the control unit (26) also regulates the source of current (24, 24A, 24B; 44, 46) to control current through the coil (22; 40, 42) so the coil (22; 40, 42) is magnetically coupled to the valve body (18) in the other of the closing and opening directions.

3. The directional valve according to claim 1 or 2, characterised in that the valve body (18) contains a permanently magnetised ferromagnetic material.

4. The directional valve according to any of the above claims, characterised in that the control unit (26) regulates the source of current (24; 44, 46) on the basis of inductive sensing of the valve body's (18) position and/or the EMF generated in the coil (22; 40, 42) by the valve body's (18) movement or deformation and/or the change in inductance caused by the valve body's (18) deformation.

5. The directional valve according to any of the above claims, characterised in that the control unit (26) regulates the source of current (24, 24A, 24B; 44, 46) on the basis of a pressure gradient obtained from measurement values supplied by a first pressure gauge (34; 36), arranged to measure pressure on the directional valve's (12; 14) inlet side, and a second pressure gauge (36; 38), arranged to measure pressure on the directional valve's (12; 14) outlet side.

6. The directional valve according to any of the above claims, characterised in that the control unit (26) regulates the source of current (24, 24A, 24B; 44, 46) on the basis of the flow through the directional valve as determined from measurement values supplied by a flow meter (30; 32) arranged to measure flow through the directional valve (12; 14).

Drawing